Sementina: the rockfall that closed the cantonal road was a known risk

On Friday 9 October, a boulder broke loose from the slope above the cantonal road in Sementina, in the Bellinzona area, and struck a passing car. No one was injured, but the road had to be closed for about four hours, causing major traffic disruption in the area.

The fallen material came from a point roughly 30 metres above the roadway. Crews worked until midnight to clear around twenty cubic metres of debris, including boulders weighing about three tonnes each. In the following days, the road was secured with concrete blocks and protective nets.

According to cantonal geologist Jean Frédéric Kauffmann, a lever effect was behind the collapse: «Si è trattato di un effetto leva esercitato da una radice» (it was a lever effect caused by a root), he explained. The effect was worsened by soil swelling and saturation after recent weeks' rain. Kauffmann describes the episode as limited in scale, but says it must be taken seriously because the stretch of road is heavily used.

A known risk

Along the same cantonal road, toward Gudo, similar landslides had already occurred in past years. The hazard was therefore no surprise to the authorities. Protective nets had already been installed above homes in the building zone, while the risk above the road itself had been judged acceptable.

Kauffmann says the protection criteria will not change, but that the hazard analysis will need to be updated in light of what happened. The cantonal geologist also notes that climate change is increasing the frequency and intensity of such events, and that authorities now have far more detailed records than in the past, allowing for a more accurate assessment of risk.

What remains unclear is what resources Ticino will use to update the mapping of at-risk slopes along its busiest roads, and what concrete measures will follow for those who live in or travel daily through these exposed areas.